Incendiary composition containing white phosphorus and hexamethylenetetramine



United States atent O 3,441,955 INCENDIARY COMPOSITION CONTAIN- INGWHITE PHOSPHORUS AND HEXA- METHYLENETETRAMINE Samuel Sass, Bel Air,Benjamin Witten, Baltimore, and Paul Davis, Bel Air, MIL, assignors tothe United States of America as represented by the Secretary of the ArmyN Drawing. Filed Aug. 25, 1967, Ser. No. 663,443 Int. Cl. C06d 1/02 US.Cl. 149-30 7 Claims ABSTRACT OF THE DISCLOSURE DEDICATORY CLAUSE Theinvention described herein may be manufactured, used, and licensed by orfor the Government for governmental purposes without the payment to usof any royalty thereon.

SPECIFICATION This invention relates to a formulation which employswhite phosphorus as the initiator of burning, to ignite a combustiblesolid in order to propagate heat (flame). The combustible mixture burnsspontaneously on exposure to air and produces a considerably moreeflicient incendiary than white phosphorus alone.

While white phosphorus has been successfully used in the production ofscreening smoke in a variety of formulations, it has not been effectivein starting fires. The explanation has been offered that thisineffectiveness is due to poor heat transfer; one reason for which isthe deposit of phosphorus pentoxide on the burning surface. Whitephosphorus, unless near its melting point or unless disseminated as fineparticles, will smolder rather than flame, and this gradual burningdissipates potential heat and decreases the use of the material as anincendiary. Plasticized white phosphorus (PWP), a mixture of whitephosphorus (WP) and GR-S rubber, effectively coats particles ofphosphorus and, on explosive dissemination, causes slower burning andreduces pillaring. While the WP and GR-S mixture increases elfectivenessas a screening smoke, the efiiciency as an incendiary is furtherreduced.

The object of this invention is to more effectively utilize the ignitionproperties of white phosphorus in air whereby it serves as both aninitiator or fuze and as a contributor to the overall heat energy of asystem.

Other objects of and uses for the invention will be obvious and appearhereinafter in the following detailed description.

Our combustible mixture can be utilized in any type of munition; whetherthe combustible material is mechanically or explosively disseminated.

In accordance with our invention, mixtures by weight of white phosphorusto hexamethylenetetramine of 80:20, 50:50, and 20:80 were compounded inan air-tight vessel under nitrogen. In compounding the mixture,hexamethylenetetramine (HMTA) of the desired weight was placed 3,441,955Patented Apr. 29, 1969 "ice in a test tube, Erlenmeyer flask, or similarvessel and the weighed increment of WP added. The vessel, after blowingin a head of oxygen-free nitrogen, was sealed by means of a flexiblerubber tubing closed with a one holed rubber stopper containing a glassrod for mixing, and the vessel was placed in an oil bath heated toapproximately 50 C. When the WP had melted, the mixture was trituratedto uniformity by means of the freedom of movement of the glass rod inthe rubber tubing. The trituration could also have been accomplished bymeans of a slowly rotating sealed mechanical stirrer or other equivalentmeans. The container was removed from the oil bath and triturationcontinued to room temperature (25 0.). Upon completion of trituration,the mixture was transferred to a polyethylene bag purged free of oxygenby means of a stream of nitrogen or carbon dioxide gas while under anoxygen-free atmosphere. While in the bag, the mixture was shaped intorods, pellets, or balls; the rods being formed by extrusion throughglass tubing, the pellets by extrusion through glass tubing and slicingwith a knife to the desired dimensions, and the balls by hand shaping.While the shaping procedure was carried out manually by placing theshaping instruments within the bag at the time the mixture was placedtherein and worked by grasping the outside of the bag, the procedurecould also be automated. After shaping was completed, the material wastransferred to screw-cap bottles while still in the oxygen-free bag.

In principle, the pelleted or caked material, when exposed to air,presents white phosphorus in an exposed form. The phosphorus reacts withoxygen by a well known reaction to form phosphorus pentoxide whileevolving heat. HMTA, which is in close contact with the whitephosphorus, is ignited and, in burning, produces gaseous products whichcontinue to evolve and prevents the coating of residual unburned surfacewith phosphorus pentoxide or ash (if another combustible solid is alsoincorporated as fuel). In this manner, continuous burning of thephosphorus and added fuel is maintained under flame rather than undersmoldering conditions.

EXAMPLE 1 WP was compounded with HMTA in varying compositions. A mixtureof WP by weight and 20% HMTA by weight, when pelleted and exposed toair, burned spontaneously and ignited paper of cardboard consistency.Mixtures of 50:50 by weight and 80 HMTA:20 WP by weight in pellet form,burned with a smaller flame and left more ash but ignited paper andcotton fabric. The increased quantity of HMTA in proportion to WPproduced a longer burning mixture but with smaller flame. The adjustmentof the mixture could allow programming of any desired effect.

Pellets of 2 cm. diameter and 1 cm. thickness were formed by extrusionthrough a tube of the same internal diameter under hand pressure andunder nitrogen, and the resulting material was sliced to the desireddimensions by means of a knife. The pellets were placed and sealed intosmall, thin-walled glass vials equipped with screw-cap tops. Since thefabrication and filling was performed under nitrogen, the extrusion tubealso contained a nitrogen atmosphere. The mixture could have beenencapsulated in a brittle resin as well as in glass. Ten ampoules, thusprepared and enclosed in glass in an oxygen-free atmosphere, when thrownagainst a hard surface (rock, concrete, and wood), ruptured and producedspontaneous flame. Where wood, paper, or dry vegetation were exposed,these were ignited.

The mixture of 80% WP:20% HMTA by weight burned spontaneously and with arapidly burning large flame. A 50% by weight mixture of WP-HMTA ignitedonly slightly less rapidly but produced a longer burning small flame.This mixture also ignited combustile mate rial with which it was incontact. A mixture of 20% WP:80% HMTA by weight flamed within severalseconds, produced only a pellet surface flame and longer burning butmore ash. This latter also ignited materials such as paper.

EXAMPLE 2 Mixtures were compounded of WP, HMTA, or other material whichburns with evolution of gases, and other combustible solid selected toimpart properties desired in a particular incendiary system; such ashigher burning temperature (over 700 C.) or longer burning. Among thesecould be thermite types (aluminum, magnesium) for higher temperatureflame or paper pulp, cellulose, high melting point hydrocarbons (atleast 60 C.) or similar combustible but non-explosive materials forlonger burning.

Pellets of the size described in Example 1, containing 30% by weight ofWP, 40% by Weight of HMTA and 30% by weight of ashless paper pulp,ignited within 5 seconds, burned with only a surface flame, producedblack smoke, had a longer burning time than any of the mixture describedabove, and ignited paper with which it came in contact.

EXAMPLE 3 A mixture of WP, HMTA or other combustible and gas producer,and an explosive of comparatively low shock and heat sensitivity as fueland as an explosive force was compounded. In this system, WP serves asthe initiator (igniter), HMTA or other material as the sensitizer-gasproducer and the explosive as a means of more widely disseminating theflame. This mixture could be embodied in a larger sized pellet. Anothervariation of this formulation would be a core of explosive surrounded bythe WPHMTA (or equivalent) mix. In the latter system, the burning outersection could be programmed to cause detonation at a given time toproduce a combined incendiary-explosion system.

We claim:

1 A. chemical composition comprising a mixture of white phosphorus andhexamethylene tetramine.

2. The composition of claim 1 wherein the white phosphorus percentcomposition is in the range of 2080'% by weight and the hexamethylenetetramine is in the range of 80-20% by Weight.

3. The composition of claim .1 wherein the mixture contains a substanceselected from the group consisting of aluminum and magnesium to producea high temperature flame.

4. The composition of claim 1 wherein the mixture contains a substanceselected from the group consisting of paper plup, cellulose, and highmelting point hydrocarbons to produce longer burning.

5. The composition of claim 4 consisting essentially of a mixture of 30%by weight of white phosphorus, by weight of hexamethyltetramine and 30%by weight of ashless paper.

6. The chemical composition of claim 1 for use as an incendiary agent.

7. The chemical composition of claim 1 for use in a munition.

References Cited UNITED STATES PATENTS 1,011,650 12/1911 Staier 149--291,092,408 4/1914 Staier 149-29 2,574,466 11/1951 Clay et al 14929 X2,658,874 11/1953 Clay et al. 149-29 X 3,183,132 5/1965 Kaye 14929 X3,193,422 7/1965 Buck et al. 14929 3,314,836 4/1967 Lachs 149-29 S. J.LECHERT, Assistant Examiner.

US. Cl. X.R. 14929

